The objectives of the total project are to determine the role of lymphocytes in the host defense against viral infections and in the development of long lasting immunity. In the current year we have attempted to identify the mechanism by which the host defends itself against viral infections that affect the immune system. A careful disection of the immune and non-immune functions affected by silica, an agent which increases susceptibility of the murine host to 17D virus, was undertaken and completed. A new in vivo assay for cell mediated immunity was needed and one developed. Finally, a new virus (cytomegalo) model was developed in which the depressive effects of the virus on the host functions could be aborgated by statolon, an interferon inducing, immunostimulative agent, and the host thereby protected against the prior inoculation of an otherwise LD100 dose of virus.